The ultimate translational goal of my research is to discover critical knowledge of basic enteric nervous system and gastrointestinal mucosal immune system biology that will improve the treatment and quality of life of children with acquired or inherited gastrointestinal disease. The focus of this proposal is to develop a scientific foundation by expanding upon my background in cell biology and neuro-immune interaction through a mentored phase of study of enteric nervous system development and gastrointestinal mucosal immune function. The Mentored Clinical Scientist Research Career Development Award will provide me with the protected time to train in the areas of enteric nervous system and immune system development and study their role in gastrointestinal mucosal immunity. I will be mentored by Dr. Ken Kudsk, a world expert in gut mucosal immunology, and Dr. Miles Epstein, a world expert in enteric nervous system development, Dr. Will Burlingham, a world expert in autoimmunity, development of tolerance, and lymphocyte function, and Dr. Chris Coe, a world expert in neuro-immunomodulation during development and aging. Each of these individuals has experience in mentoring young scientists and will guide me in my Career Development. The research plan crafted by Drs. Kudsk, the mentorship team, and myself will contribute substantially to my development as an independent researcher. We will investigate a potential developmental link between the enteric nervous system and gastrointestinal mucosal immunity. Hirschsprung's disease (HSCR) is a congenital segmental absence of the enteric nervous system (ENS) in the distal gut that results from failure of neural crest cell migration to the distal hindgut and is invariably lethal if untreated. Although HSCR can be surgically treated with segmental resection of the aganglionic bowel, up to 60% of patients in both the pre- and post-operative periods develop life-threatening Hirschsprung's-associated enterocolitis (HAEC), the pathophysiology of which is poorly defined. We have performed preliminary studies in animals with a neural crest-specific deletion of EdnrB (EdnrB-null) that exhibit distal colonic aganglionosis and closely model human, neonatal HSCR. These animals develop HAEC and die by post-natal day 28. Our preliminary results indicate that EdnrB-null mice have smaller Peyer's Patches with fewer mature B-lymphocytes than their heterozygote littermates. Additionally, the EdnrB- null animals have decreased amounts of small bowel secretory immunoglobulin A (SIgA), which is the key effector of mucosal immune defense. Finally, microarray analysis of embryonic tissue indicates decreased expression of genes involved in B-lymphocyte function in EdnrB-null mice. We hypothesize that deletion of EdnrB in the neural crest results in altered endothelin expression outside the neural crest and defective B- lymphocyte development and/or function, resulting in increased susceptibility to HAEC. In order to test this hypothesis, we will (Aim 1) determine if expression of the endothelin axis in developing hematopoietic organs is altered in animals with a neural crest-specific deletion of EdnrB, (Aim 2) determine if neural crest specific deletion of EdnrB results in intrinsic or extrinsc defects in B-lymphocyte function, and (Aim 3) determine the extent of the contribution of physiologic stress to the development of the EdnrB-null immune phenotype. We expect that these studies will provide insight into potential immunomodulatory targets for prevention and treatment of Hirschsprung's-associated enterocolitis. Completion of these aims ensures that there will be a clearer understanding of the underlying mechanisms in HAEC and the relationship between enteric nervous system and gastrointestinal mucosal immune development. The long-term goal of our research is to gain an understanding of the interactions between the enteric nervous system and gastrointestinal immune system in both development and disease to permit the generation of novel neuro-immunomodulatory therapies that may potentially target a broad range of congenital and acquired pediatric gastrointestinal tract diseases.